The present invention is directed to an apparatus for assembling a tension tie member made up of individual tension elements, such as steel wires, strands and the like, and arranged within a tubular sheathing. The tension elements are inserted individually and successively through conically shaped boreholes in an anchor plate into the tubular sheathing and the tension elements are anchored in the plate by multi-part annular wedges. The invention is also directed to the method of assembling and anchoring a tension tie member in a structure, such as a diagonal cable in a stayed girder bridge.
Tension tie members, such as are used in civil engineering for anchoring different parts of a structure, such as diagonal cables in stayed girder bridges or the like, frequently are made up of a bundle of individual parallel tension elements, such as steel wires or strands, arranged together in the unsupported area of the tension tie member between the parts of the structure and enclosed within a tubular sheathing. The tension tie member is guided through the parts of the structure in a passageway or duct so that the tie member is longitudinally or axially movable and the opposite ends of the tie member are anchored on the outsides of the parts of the structure relative to the sides between which the tie member extends. Anchor members include an anchor plate with conically shaped boreholes through which the individual elements are inserted and in which they are anchored by multi-part annular wedges. The tubular sheathing can be formed in the unsupported region between the parts of the structure by a plastics material tube, such as a polyethylene tube, or a steel pipe. In the region of the anchorage usually a steel anchor tube is employed. The space within the tubular sheathing around the individual tension element is grouted after the elements are tensioned. Either an anti corrosive substance can be used in the grouting operation or a hardenable material, such as a cement mortar. A tension tie member of this type remains post-tensionable and replaceable after the grouting operation.
As is particularly the case in diagonal cables of stayed girder bridges, difficulties are involved in installing heavy cables in the required diagonal position between anchorages in the roadway girder and in the bridge tower, because of the great height involved. If the diagonal cables are assembled on a working plane, such as the roadway slab of a completed bridge section, then the cables must be lifted into the required diagonal position using lifting apparatus and simultaneously threading the tie member into the lower and upper anchorages. It is also possible to provide a diagonal template mounted on scaffolds for the installation of the diagonal cable and to thread the individual tension elements through the tubular sheathing and the anchor members while the cable is supported on the template. All of the individual tension elements are tensioned simultaneously in such an arrangement. To reduce the costs involved and to simplify the procedures for installing diagonal cables it has been known first to thread only one tension element into the tubular sheathing placed on a working plane and then to insert the tension element into the anchoring members already in place and to tension the element. In this procedure, the tubular sheathing is arranged in an inclined but straight position extending between the two anchor members, note West German Offenlegungsschrift No. 31 38 819. Subsequently, the rest of the individual tension elements are installed and anchored, in each instance, after tensioning.
When a diagonal cable is assembled in this manner it is difficult in the unsupported region of the cable to push the individual tension elements through the often very long tubular sheathing without having the elements become jammed in an inaccessible location. In the anchor region difficulties occur in placing, at first, the unordered position of the individual tension elements within the tubular sheathing to correspond with the arrangement in the anchor members, that is, threading the individual elements into the conically shaped boreholes in the anchor plate accompanied by the spreading of the elements. In a known method this problem was solved by providing ducts adjoining the anchor plate and extending over the length of the spreading region with the ducts being in the form of additional sheathing tubes with an opening provided in front of the ducts so that each individual tension element can be individually threaded into a duct so that it passes directly into the corresponding borehole in the anchor plate when it exits from the duct.
Another problem experienced in assembling diagonal cables along a diagonal path is that the work must be carried out against the force of gravity when the individual tension elements are inserted in an upward direction, that is, a greater expenditure force is required. When the individual tension elements are inserted in the downward direction, it is necessary to secure the individual elements against slipping after they are inserted and before they are cut off. The securement of the tension element is effected by wedges also required for the anchoring operation, however, it is necessary that the wedges are placed on the individual elements at the commencement of the insertion step and each element must be pushed through the corresponding wedge. This movement of the element through the wedge is not possible, since the individual sections of the annular wedges are provided with teeth on the interior for securing the elements and the teeth damage the surface of the elements when they are passing through them. Theoretically, the annular wedges made up of a plurality of sections, preferably three sections, are held together by a spring ring so that the wedge could be taken apart and installed from the side of the element, such an operation would require additional assemby manipulations.